[QUOTE=operator;10403835]I would absolutely not drill through a threadless stem in the fashion you're suggesting. There's no need anyways, you can get a "fork mounted" canti stop. Specialized makes one. It attaches to the front of the fork.
Are you aboslutely sure you cannot fit one of these in the headset? All you have to have is even just one spacer for example this to fit:
[/QU
The problem is that the top of the Mavic headset is a cup that screws down and overlaps the entire unit.
Am I correct that the unit you describe requires a drilled fork, which this fork is not.